WO2021255490A1

WO2021255490A1 - A method of forming a smart card, a prelam body, and a smart card

Info

Publication number: WO2021255490A1
Application number: PCT/IB2020/000576
Authority: WO
Inventors: Christophe Mathieu; Christophe PAUL; Simon VASSAL
Original assignee: Linxens Holding
Priority date: 2020-06-18
Filing date: 2020-06-18
Publication date: 2021-12-23

Abstract

The present invention provides, in various aspects, a method of forming a smart card, a prelam body, and a smart card. In some illustrative embodiments, a smart card having at least one feature module integrated therein, is formed, wherein a substrate having at least one first landing pad formed thereon is prepared, a solder material is formed on the at least one first landing pad, the substrate with the solder material on the at least one first landing pad is integrated into a prelam body, wherein the substrate is arranged at a first surface of the prelam body, the prelam body is recessed at a second surface of the prelam body opposite the first surface, wherein an upper surface of the solder material on the at least one first landing pad is exposed in a first recess of the prelam body, a first feature module is inserted into the first recess of the prelam body, and the first feature module inserted into the first recess is bonded to the prelam body so as to electrically connect the at least one first landing pad to the first feature module via the solder material.

Description

A method of forming a smart card, a prelam body, and a smart card

Field of the Invention

The present invention relates to a method of forming a smart card having at least one feature module integrated therein, and further relates to a prelam body and to a smart card with such a prelam body.

Background Art

In general, a smartcard is a physical electronic authorization device, used to control access to a resource. Typically, a smart card is provided as a plastic card in the size of a credit card formed by a card body into which one or more electric and electronic elements, such as a chip, an antenna, contact elements and the like, is integrated, wherein after the integration, the card body is referred to as a smart card. Furthermore, many smart cards include a pattern of metal contacts for electrical connection to the integrated chip and/or may be configured to allow contactless or wireless communication with the smart card. In case of a contactless smart card, one or more antenna components are integrated into a body of the smart card so as to allow contactless or wireless interaction with a chip integrated into the smart card.

In order to increase the functionality of a smart card, more and more effort is made to include an increasing number of features into a single smart card. For example, one or more security feature modules may be integrated into the card body of a smart card so as to increase the security of the smart card and/or one or more memory modules may be integrated into a smart card for storing sensitive personal data and/or means for using a smart card as a key card for accessing personal belongings such as a house, a car, a room in a hotel and the like, may be integrated into a smart card. In summary, there is a wide variety of possible functional modules to be integrated into a smart card, such as a fingerprint sensor for implementing biometric cards and/or a dynamic CVV in order to implement dynamic CVV functionality, one or more chip modules, a display, battery modules, antenna modules and the like. In a conventional integration process, a lead- frame chip module may be integrated into a card body by inserting the lead-frame chip module into a recess formed in the card body and attaching the lead-frame chip module to the card body by an adhesive, for example.

When including a great number of features into current smart cards, a high number of interconnections becomes necessary. For example, when realizing a contactless smart card having biometric security features, it may be possible that up to twenty interconnections between a printed circuit board and feature modules realizing contactless and biometric features, are required. Despite an increasing number of features integrated into a smart card, a high quality of electrical interconnection among integrated features and integrated circuits in a card body, as well as a reliably interconnection over a long lifetime of a smart card is to be ensured.

However, it is not efficient to provide a high number of copper pads as interconnections on a card body. In conventional pick-and-place processes, a placement of copper pads is not sufficiently accurate when considering all the dimensional changes, which occur to a card body during the various stages in a smart card fabrication process due to lamination, card cutting, card milling and embedding of one or more modules into the body. With regard to thermal compression bonding (TCB), which is employed for equipping a card body with an antenna module when realizing a wireless feature, a copper wiring of the antenna is bonded to copper pads on the card body. However, a milling of copper wires as conventionally required by TCB processes, is difficult to control.

Document EP 2871596 A1 shows an interconnected electronic device comprising at least a first electronic or electrical component comprising at least a first interconnection pad, the electronic device further comprising an electronic or electrical circuit provided with at least a second pad interconnection. The electronic device further comprises an intermediate electrical interconnection wedge between each of the first and second interconnection pads.

Document WO 01/45039 A1 shows a method for producing a chip card comprising a module with contacts that are flush with the surface of the body of a card. The method further comprises manufacturing a printed circuit board, on which electronic and/or electric components are fixed, integration of the integrated circuit board into the body of the card, and connecting the contact module to the printed circuit board by means of interconnecting blocks implanted on the printed circuit board.

In view of the above discussed situation, it is an object of the present invention to provide a method of forming a smart card which is easily employed in continuous reel-to-reel processes, providing a high quality of electrical interconnection between feature modules and integrated circuits of a card body. A further objective of the present invention is to provide a prelam body and a smart card having at least one feature module integrated therein, the at least one feature module being reliably interconnected.

Brief Summary

The above problems are solved in the various aspects of the present invention. Some aspects relate to a method of forming a smart card as defined in claim 1, a prelam body as defined in claim 18, a smart card as defined in claim 22, and a smart card as defined in claim 25. More advantageous embodiments are defined in the dependent claims 2 to 17, 19 to 21, 23 to 24 and 26 to 27.

In a first aspect of the present invention, a method of forming a smart card having at least one feature module integrated therein, is provided. In accordance with illustrative embodiments of the first aspect, the method comprises preparing a substrate having at least one first landing pad formed thereon, forming a solder material on the at least one first landing pad, integrating the substrate with the solder material on the at least one first landing pad into a prelam body, the substrate being arranged at a first surface of the prelam body, recessing the prelam body at a second surface of the prelam body opposite the first surface, wherein an upper surface of the solder material on the at least one first landing pad is exposed in a first recess of the prelam body, inserting a first feature module into the first recess of the prelam body, and bonding the first feature module inserted into the first recess to the prelam body so as to electrically connect the at least one first landing pad to the first feature module via the solder material. By means of the solder material formed on the at least one first landing pad prior to integrating the substrate with the solder material into a prelam body and recessing the prelam body for forming a first recess, into which a first feature module is inserted and bonded, a reliable connection of the prelam body and the first feature module is obtained, independent of any height or thickness of the landing pad provided on the substrate. Herein, the exposed upper surface of the solder material on the at least one first landing pad in the first recess of the prelam body is used for bonding the first feature module to the prelam body. Furthermore, the solder material compensates for differences in the thickness of the landing pad and the feature module despite of the thickness of a body of the smart card being fixed by an ISO standard.

Regarding the expression “prelam body”, the prelam body as referred to in this description, is understood as representing a prelaminated body with multiple layers of an insulating material, such as PVC, pre-laminated together. This prelaminated body represents an intermediate product obtained during fabrication of a smart card. For example, an illustrative prelam body may be obtained by fusing together different layers of a thermoplastic material into a single homogeneous sheet body, thereby embedding a substrate with at least one landing pad, e.g., a PCB substrate, a flexible substrate and the like, into the prelam body.

Regarding the expression “body of a smart card”, this expression as referred to in this description, means a physical body of a smart card. For example, depending on the stage during fabrication of a smart card, the body of a smart card at a given stage during fabrication represents the physical body of the smart card at the given stage during fabrication which only comprises physical elements which physically constitute the smart card at the given stage during fabrication. In another example, a body of a finalized smart card may be understood as comprising the prelam body and at least one feature module integrated therein.

In a first illustrative embodiment of the first aspect, the method may further comprise providing the first feature module with an anisotropic conductive film on the surface of the first feature module prior to inserting the first feature module into the first recess, wherein the anisotropic conductive film covers at least one contact pad provided in the surface of the feature module. The method may further comprise bringing the anisotropic conductive film into contact with the exposed upper surface of the solder material on the at least one first landing pad when inserting the first feature module into the first recess. Due to using the anisotropic conductive film, electrical and mechanical connection may be provided because of the electrical conductivity and adhesion properties of the anisotropic conductive film.

In accordance with some illustrative examples of the first embodiment of the first aspect, the bonding of the first feature module to the prelam body may comprise curing the anisotropic conductive film in the first recess at an elevated temperature of at least 160°C. Accordingly, a reliable mechanical bonding of the first feature module and the prelam body is achieved. In some explicit examples herein, the first feature module may be subjected to a bonding pressure when curing the anisotropic conductive film. Accordingly, a reliability of the mechanical connection may be further increased.

In accordance with some illustrative examples of the first embodiment of the first aspect, the solder material may be a high temperature solder material, a material fusible at temperatures greater than 160°C. For example, the solder material may be fusible at temperatures higher than the elevated temperature at which the anisotropic film is cured. Accordingly, a reliable electrical connection between the first feature module and the prelam body may be ensured.

In accordance with a second illustrative embodiment of the first aspect, the first feature module may have at least one first contact pad exposed on a surface of the first feature module, the method further comprising aligning the at least one first contact pad of the first feature module to the at least one first landing pad of the prelam body prior to inserting the first feature module into the first recess. Accordingly, a reliable electrical connection between the first feature module and the at least one first contact pad may be ensured when properly aligning the contact pad relative to the at least one landing pad in the first recess and the exposed upper surface of the solder material in the first recess.

In accordance with a third illustrative embodiment of the first aspect, a height of the solder material and the at least one first landing pad may be at least 100 pm before milling. For example, the thickness of the landing pad may be 20 pm at least and the thickness of the solder material may be 80 pm at least, the solder material being used as a buffer material for height adjustment. In this way, a reliable contacting of the first feature module and the at least one first contact pad may be ensured in the prelam body, independent of a size of the first contact pads and a size of the first feature module.

In accordance with a fourth illustrative embodiment of the first aspect, the method may further comprise forming at least one second landing pad in electrical contact with the integrated circuit on the substrate and forming a solder material on the at least one second landing pad prior to integrating the substrate into the prelam body, recessing the prelam body at the second surface of the prelam body for forming a second recess in the prelam body, wherein an upper surface of the solder material on the at least one second landing pad is exposed in the second recess, inserting a second feature module into the second recess of the prelam body, and bonding the second feature module inserted into the second recess to the prelam body. Accordingly, a reliable mechanical and electrical connection between the prelam body and first and second feature modules is ensured, independent of sizes of the first and second feature modules.

In accordance with some illustrative examples of the fourth embodiment of the first aspect, the first and second feature modules may be of different thicknesses, the first recess having a first depth and the second recess having a second depth different from the first depth. The first and second depth may be such that the first and second feature modules may be accommodated into the first and second recesses so as to realize a smooth surface of the body of the smart card at the first and second feature modules. Accordingly, a variety of different feature modules may be integrated into a common prelam body, independent of thicknesses of the feature modules.

In accordance with some illustrative examples of the fourth illustrative embodiment of the first aspect, the solder material on the at least one first and second landing pad may have a common height in the prelam body prior to the recessing. In this way, the solder material may be easily disposed on the substrate, for example, by a printing process, during an automated fabrication process.

In accordance with some illustrative examples of the fourth embodiment of the first aspect, the method may further comprise providing the second feature module with anisotropic conductive film on the surface of the second feature module prior to inserting the second feature module into the second recess and bringing the anisotropic conductive film into contact with the exposed upper surface of the solder material on the at least one second landing pad when inserting the second feature module into the second recess. Due to the anisotropic conductive film, electrical and mechanical connection may be reliably provided in the second recess. For example, the bonding of the second feature module to the prelam body may comprise curing the anisotropic conductive film in the second recess at an elevated temperature of at least 160°C. Accordingly, the reliability of the connection in the second recess may be increased. For example, the second feature module may be subjected to a bonding pressure when curing the anisotropic conductive film. Accordingly, the reliability of the connection in the second recess may be further increased.

In accordance with some illustrative examples of the fourth embodiment of the first aspect, the solder material may be a high temperature solder material, fusible at temperatures greater than 160°C. For example, the solder material may be fusible at a temperature higher than the elevated temperature at which the anisotropic conductive film is cured. Accordingly, a reliable connection may be ensured.

In accordance with some illustrative examples of the fourth embodiment of the first aspect, the second feature module may have at least one second contact pad exposed on a surface of the second feature module, the method further comprising aligning the at least one second contact pad of the second feature module to the at least one second landing pad of the prelam body prior to inserting the second feature module into the second recess. Accordingly, a reliable electrical connection between the second feature module and the at least one second contact pad may be ensured when properly aligning the contact pad relative to the at least one landing pad in the second recess and the exposed upper surface of the solder material in the second recess.

In accordance with some illustrative examples of the fourth embodiment of the first aspect, a height of the solder material and the at least one second landing pad may be at least 100 pm. For example, such a height may be given by a total thickness formed by a thickness of a landing pad and a thickness of solder material. In this way, a reliable contacting of the second feature module and the at least one second contact pad may be ensured in the prelam body, independent of a size of the second contact pads and a size of the second feature module.

In accordance with a fifth embodiment of the first aspect, the substrate may be a flexible substrate, having an integrated circuit formed therein. A flexible substrate may be thinner when compared to a rigid printed circuit board, thereby allowing to reduce a size of a prelam body and allowing easier integration into the prelam body with less risks to have a non-ISO total thickness of the smart card and with less issues caused for aesthetic reasons.

In a second aspect, a prelam body is provided. In accordance with illustrative embodiments of the second aspect, the prelam body comprises a substrate at a first surface of the prelam body, the substrate having at least one first landing pad and a solder material disposed on the at least one landing pad, at least one layer of insulating material into which the at least one first landing pad and the solder material is completely embedded, and a first recess formed in a second surface of the prelam body, the second surface being opposite to the first surface, wherein the first recess only exposes an upper surface of the solder material on the at least one first landing pad. Accordingly, in the recess in the at least one layer of the insulating material of the prelam body, there is only the solder material exposed and the at least one first landing pad remains completely embedded into the at least one layer of insulating material. In current technologies, landing pads have typically a thickness of 18 pm, 35 pm or 70 pm and a thickness of a card body (i.e., the body of a smart card before functional modules are integrated into the body of the smart card) may be in the range from 760 pm to 840 pm. The solder material acts as an additional material on the landing pads in the prelam body and allows to compensate for differences in the thickness of the landing pad and a feature module, which is subsequently integrated into the body of a smart card formed of the prelam body, despite of an actual thickness of a body of the smart card.

In accordance with a first embodiment of the second aspect, the substrate may be a flexible substrate having an integrated circuit formed therein. A flexible substrate may be thinner when compared to a rigid printed circuit board, thereby allowing to reduce a size of a prelam body.

In accordance with a second embodiment of the second aspect, the prelam body may further comprise at least one second landing pad formed on the substrate and a solder material disposed on the at least one second landing pad, and a second recess formed in the second surface, the second recess only exposing an upper surface of the solder material on the at least one second landing pad.

In some illustrative examples of the second embodiment of the second aspect, the first recess may have a first depth and the second recess may have a second depth, the first and second depth being different from each other. Accordingly, a variety of different feature modules having different sizes may be integrated into the prelam body, independent of thicknesses of the feature modules.

In a third aspect of the present invention, a smart card is provided. In illustrative embodiments of the third aspect, the smart card comprises the prelam body in accordance with illustrative embodiments of the second aspect or in accordance with the first embodiment of the second aspect, and a first feature module having an anisotropic conductive film formed on a surface of the first feature module, wherein the first feature module is accommodated into the first recess such that the exposed upper surface of the solder material in the first recess is covered by the anisotropic conductive film. By means of the solder material, a reliable connection of the prelam body and the first feature module is obtained, independent of any height or thickness of the landing pad provided on the substrate. Herein, the exposed upper surface of the solder material on the at least one first landing pad in the first recess of the prelam body is used for bonding the first feature module to the prelam body. Furthermore, the solder material compensates for differences in the thickness of the landing pad and the feature module despite of an actual thickness of the smart card.

In accordance with a first embodiment of the third aspect, a height of the solder material together with the at least one first landing pad may be in the range from about 50 pm to about 250 pm.

In a second embodiment of the third aspect, the smart card may further comprise a lamination layer covering the first surface of the prelam body such that the substrate is sandwiched between the lamination layer and the at least one insulating layer, and an electrical component. The electrical component being arranged on the surface of the first feature module, wherein the first recess has a cavity formed at a portion of a bottom surface of the first recess, the cavity extending at least partially through the substrate and accommodating the electrical component, wherein the electrical component is left uncovered by the anisotropic conductive film. Accordingly, a thickness of the smart card may be kept small, even when integrating feature modules having components protruding from a surface of the feature module to a greater extent than contact pads on the feature module, into the prelam body.

In a fourth aspect, a smart card is provided. In accordance with illustrative embodiments of the fourth aspect, the smart card comprises the prelam body of the second illustrative embodiment, and a second feature module having an anisotropic conductive film formed on a surface of the second feature module, wherein the second feature module is accommodated into the second recess such that the exposed upper surface of the solder material in the second recess is covered by the anisotropic conductive film.

In a first embodiment of the fourth aspect, a height of the solder material together with the at least one second landing pad may be in the range of about 50 pm to about 250 pm.

In a second embodiment of the fourth aspect, the solder material may be a high temperature solder material usable at temperatures greater than 160°C.

Brief Description of the Drawings

Further aspects and illustrative embodiments of the present invention will be described in greater detail in connection with the accompanying drawings in the detailed description below, wherein the drawings are not to scale.

Figs. 1 to 6 schematically illustrate, in cross sectional views, various stages during formation of a smart card in accordance with some illustrative embodiments of the present disclosure; and Figs. 7 to 9 schematically illustrate, in cross sectional views, various stages during formation of a smart card in accordance with some other illustrative embodiments of the present disclosure.

Detailed Description

With regard to Figs. 1 to 6, various stages during formation of a smart card having at least one feature module integrated therein will be described. A smart card 100 resulting from such a formation is shown in Fig. 6.

Referring to Fig. 1, an initial stage during formation of the smart card 100 in Fig. 6 is schematically illustrated. At the stage illustrated in Fig. 1, a substrate 10 having at least one first landing pad (shown in terms of a landing pad 12 and a landing pad 14 formed on the substrate 10), is prepared. Despite of the landing pad 12 and the landing pad 14 being explicitly shown in Fig. 1 , this does not pose any limitation on the present disclosure and the person skilled in the art will appreciate that a single landing pad or more than two landing pads may be provided instead, e.g., up to ten landing pads or more than ten landing pads, such as twenty landing pads etc.

In accordance with some illustrative embodiments, the substrate 10 may be a flexible substrate as employed in the technology of flexible electronics orflexible circuits. Forexample, the substrate 10 may be a flexible glass-epoxy substrate or a plastic substrate, such as a substrate made of at least one of polyimide, PET, PEN, PC, PVC, and paper. However, this does not pose any limitation to the present disclosure and the substrate 10 may be a substrate as employed in the techniques of printed circuit boards, i.e. , a rigid substrate.

In accordance with some illustrative embodiments of the present disclosure, the substrate 10 may comprise an integrated circuit (not shown), the integrated circuit implementing a microprocessor, a memory and/or a crypto processor. The landing pads 12 and 14 may be provided as external contacts to the integrated circuit (not illustrated) integrated into the substrate 10.

For example, in case that the substrate 10 is a flexible substrate, at least one flexible printed circuit (FPC) may be integrated into the substrate 10. The FPC may comprise a base laminate with 1 or 2 layers of copper (between 9 pm and 200 pm) and may be made with a photolithographic and chemical etching technology or, in an alternative way with a mechanical punching of the copper foils before lamination on the base laminate.

With regard to Fig. 2, the substrate 10 is schematically illustrated in a more advanced stage during formation of the smart card, wherein a solder material 16 is formed on the landing pad 12 and a solder material 18 is formed on the landing pad 14. In accordance with some illustrative examples herein, the solder material 16 and 18 may be deposited via a solder printing process onto the substrate 10. Furthermore, a reflow process may be performed after the solder printing process for reflowing the solder material 16, 18 on the landing pads 12, 14. In accordance with some illustrative examples herein, printing and reflowing of the solder material 16, 18 may be easily done in any continuous reel-to-reel process with a desired thickness, e.g., a thickness of at least 100 pm, by screen printing. This thickness may be a total thickness formed by a thickness of a landing pad 12 / 14 and a thickness of the solder material 16 / 18. In accordance with some special illustrative examples herein, the solder materials 16, 18 may be given by a high temperature solder paste, such as SAC305, for example (which is a solder paste made out of 96.5 weight% Sn, 3.0 weight% Ag, and 0.5 weight% Cu) or the like. Such a solder paste made of SAC305 may have a melting point of about 217°C. This does not pose any limitations of the present disclosure and a high temperature solder paste that has a melting point of at least 160°C may be employed instead. Preferably, the solder material 16, 18 may have a reflow temperature which is higher than any elevated temperature to which the substrate is exposed during subsequent processing, i.e. , after the stage illustrate in Fig. 2 is completed. For example, the solder material 16, 18 may have a reflow temperature of about 250°C or more.

In accordance with some illustrative embodiments, the solder material 16 may be formed on the landing pad 12 such that the solder material 16 and the landing pad 12 together may have a height of at least 100 pm after printing and reflow processes are performed. Similarly, the solder material 18 may be formed on the landing pad 14 such that the solder material 18 and the landing pad 14 together have a height of at least 100 pm after printing and reflow processes are performed.

Referring to Fig. 3, a more advanced stage during formation of the smart card is shown, wherein the substrate 10 with the solder material 16, 18 on the landing pad 12, 14 is integrated into a prelam body 20. In accordance with some illustrative examples herein, an integration of the substrate 10 into the prelam body 20 may include an embedding of the solder material 16, 18 and the landing pads 12, 14 on the substrate 10 into at least one layer 22 of insulating material. In accordance with some illustrative examples, the at least one layer 22 of insulating material may represent one or more layers of insulating material which are formed on the substrate 10 so as to completely embed the solder material 16, 18 and the landing pads 12, 14 into the prelam body 20 of Fig. 3.

In accordance with some illustrative examples, the at least one layer 22 of insulating material may represent a plurality of different layers of a thermoplastic material which is fused together into a single homogenous sheet body, sealing hermetically the solder material 16, 18 and the landing pads 12, 14 on the substrate 10. As possible materials for the at least one layer 22 of insulating material, materials such as PVC, PC, PET-G or Teslin® or stone paper may be used. The at least one layer 22 of insulating material, may be formed on a front side of the substrate, i.e., a side of a substrate 10 on which the landing pads 12 and 14 are arranged. Accordingly, the front side of the substrate 10 may be completely covered by the at least one layer 22 of insulating material.

Referring to Fig. 3, the prelam body 20 may further comprise a lamination layer 24, which is formed on a backside of the substrate 10, i.e., a side of the substrate 10 opposite the front side of the substrate 10. Accordingly, the substrate 10 may be sandwiched between the lamination layer 24 and the at least one layer 22 of insulating material. This does not pose any limitation to the present disclosure and the person skilled in the art would appreciate that the lamination layer 24 may be omitted.

With continued reference to the prelam body 20 in Fig. 3, the substrate 10 is arranged at the first surface 26 of the prelam body 20. This means that the substrate 10 is located within the prelam body 20 in a cross sectional view, such as a cross section illustrated in Fig. 3. For example, the substrate 10 may be closer to the first surface 26 than to an opposite second surface 28 of the prelam body 20. Furthermore, the front side of the substrate 10 faces towards the second side 20 and the back side of the substrate 10 faces towards the first surface 26. In case that the lamination layer 24 is omitted, the first surface 26 may be identical with the backside of the substrate 10. In case that the lamination layer 24 is present, the second surface 26 may be the back side of the lamination layer 24 opposite a side of the lamination layer 24 at which the substrate 10 is arranged.

Referring to Fig. 4, a more advanced stage during formation of the smart card is shown, wherein the prelam body 20 is recessed at the second surface of the prelam body 20 opposite the first surface 26. As a result of the recessing of the prelam body 20, an upper surface 16u of the solder material 16 on the landing pad 12 is exposed in the recess 29. Furthermore, due to the recessing, an upper surface 18u of the solder material 18 on the landing pad 14 is exposed in the recess 29. In other words, the recessing 29 is performed in order to form the recess 29 having a depth at which the upper surface 16u and the upper surface 18u are exposed. Preferably, a depth of the recess 29 is such that a height of the solder material 16, together with the landing pad 12, and a height of the solder material 18, together with the landing pad 14, respectively, are in the range from about 80 pm to 150 pm, preferably at about 100 pm.

In some alternative embodiments (not illustrated), the prelam body 20 of Fig. 3 may be further subjected to one or more processes after the stage shown in Fig. 3 is realized and before continuing with a processing as described in the context of Fig. 4 above, i.e., prior to recessing the prelam body 20 of Fig. 4. In accordance with these alternative embodiments, (not illustrated), an optional first compensation layer (not illustrated) may be formed on the first surface 26 and/or an optional second compensation layer (not illustrated) may be formed on the opposite second surface 28 of the prelam body 20 of Fig. 3. Furthermore, a bottom printed layer (not illustrated) may be formed on or over the first surface 26 and/or a top printed layer (not illustrated) may be formed on or over the second surface 28 of the prelam body 20 of Fig. 3. An accordingly formed body of the prelam body having at least one of these layers (not illustrated) formed thereon, is referred to in this description as a “card body”. In some illustrative examples, the materials used for providing the compensation layers and the printed layers may be similar to the material of the prelam layers. In these examples, lamination process may be used to deposit these layers similar to processes employed when forming the prelam layers.

Referring to Fig. 5, formation of the body of the smart card is shown at a more advanced stage during fabrication. At the stage shown in Fig. 5 and any subsequent stage, the prelam body 20 may be understood as representing a card body as explained above, although this is not explicitly stated below. Particularly, the expression “prelam body 20” in the following description may be replaced by the expression “card body” in a straight forward manner.

At the stage shown in Fig. 5, a feature module 30 is prepared, the feature module 30 having a contact pad 32 and a contact pad 34, exposed on one surface of the feature module 30. An anisotropic conductive film 36 is provided on the surface of the feature module 30, covering the contact pad 32 and the contact pad 34. The anisotropic conductive film 36 may at least partially cover the surface of the feature module 30, in any case, each of the contact pads 32 and 34 are completely covered by the anisotropic conductive film 36. Although Fig. 5 shows an anisotropic conductive film 36, this does not pose any limitation to the present disclosure and a solder material may be formed on the contact pads 32 and 34, instead, wherein the solder material is fusible at a lower temperature when compared to the solder material 16, 18.

Referring to Fig. 5, the feature module 30 is inserted into the recess 29 as indicated by two arrows in the illustration of Fig. 5, the two arrows in Fig. 5 showing a direction along which the feature module 30 is inserted into the recess 29. In accordance with illustrative embodiments, the inserting of the feature module 30 brings the anisotropic conductive film 36 on the surface of the feature module 30 into contact with the exposed upper surfaces 16u and 18u of the solder material 16, 18 in the recess 29. For example, the feature module 30 may be picked and placed by a machine so as to equip the prelam body 20 with the feature module 30 in an automated process.

In accordance with some illustrative embodiments of the present disclosure, the feature module 30 may be orientated prior to inserting into the recess 29 so as to align the contact pad 32 with regard to the exposed upper surface 16u of the solder material 16. Similarly, the contact pad 34 is aligned with respect to the exposed upper surface 18u of the solder material 18. When inserting the accordingly oriented feature module 13 into the recess 29, it may be ensured that the contact pad 32 is in alignment with the solder material 16 (and with the landing pad 12) and that the contact pad 34 is in alignment with the solder material 18 (and with the landing pad 14). In illustrative examples herein, the contact pads 32 and 34 are provided in the surface of the feature module 30 in dependence on positions of the landing pads 12 and 14 on the substrate 10. Alternatively, when forming the landing pads 12 and 14 on substrate 10, as well as when routing conductive tracks (not illustrated) of an integrated circuit (not illustrated) in the substrate 10, an arrangement of contact pads 32 and 34 of the feature module 30 is determined in dependence on a proper alignment of the landing pads 12 and 14 with respect to the contact pads 13 and 34. Furthermore, when referring to the recessing as shown in Fig. 4, the recess 29 is formed in alignment with the landing pads 12 and 14 on the substrate 10. Accordingly, an aligned accommodation of the feature module 30 with respect to the landing pads 12 and 14 on the substrate 10 may be realized.

Referring to Fig. 6, the smart card 100 is illustrated at a more advanced stage during fabrication, particularly, after inserting of the feature module 30 into the recess 29 in Fig. 5 is completed and a process of bonding the feature module 30 to the prelam body 20 is performed so as to electrically connect the landing pad 12 and landing pad 14 to the feature module 30. In the illustration of Fig. 6, an electrical connection between the landing pad 12 and the contact pad 32 as indicated by a double arrow 40 is achieved. Accordingly, a double arrow 50 indicates an electrical connection between the landing pad 14 and the contact pad 34. Therefore, the landing pad 12 is electrically connected to the contact pad 32 of the feature module 30 via the solder material 16 and the anisotropic conductive film 36. Similarly, the landing pad 14 is electrically connected to the contact pad 34 of the feature module 30 via the solder material 18 and the anisotropic conductive film 36. In this way, an arbitrary number of electrical connections between the feature module 30 and the substrate 10 may be implemented, particularly, a contacting of the integrated circuit (not illustrated) integrated into the substrate 10 with the feature module 30 by more than two interconnections involving a respective number of landing pads on the substrate 10 and in alignment therewith a corresponding number of contact pads on the surface of the feature module 30.

In accordance with some illustrative embodiments, the bonding of the feature module 30 to the prelam body 20 may comprise curing the anisotropic conductive film 36 in the recess 29 at an elevated temperature of at least 160°C and, optionally, applying a mechanical pressure to the feature module 30 relative to the prelam body 20. For example, the elevated temperature may be smaller than the temperature at which the solder material 12, 14 is fusible. In accordance with some illustrative examples, the curing together with an exerted curing pressure maybe applied for a time interval of about 5 to 20 seconds, for example, preferably in the range of 5 to 10 seconds. Accordingly, an integration of the feature module 30 into the recess 29 of the prelam body 20 maybe achieved by a combination of time, temperature and pressure. In some illustrative examples, using the anisotropic conductive film 36, a reliable electrical and mechanical connection may be obtained due to its electrical and adhesive properties.

The combination of the solder material 16 with the landing pad 12 and the solder material 18 with the landing pad 14, respectively, may provide for an associated interposer. Such an interposer may be provided in the smart card 100 of Fig. 6 in a reliable and easy way. In some examples herein, the interposer may have a thickness of at least 100 pm. When implementing such an interposer, the solder materials 16, 18 may advantageously accommodate for tolerances in the recessing process of Fig. 4, i.e. , tolerances that appear when forming the recess 29 in Fig. 4. Particularly, the process of recessing in Fig. 4 and the recess 29 in Fig. 4 do not pose the risk of damaging the landing pads 12 and 14 due to the presence of the solder materials 16 and 18 forming interposers of sufficient thickness. Accordingly, the interposers may reduce the risk of damaging the landing pads when integrating feature modules into the prelam body 20, thereby maintaining the quality of the electrical interconnection between the feature module 30 and the substrate 10 at a high level due to the solder material 16, 18 and the anisotropic conductive film 36.

In accordance with some illustrative embodiments, usage of the anisotropic conductive film 36 allows recesses with minimal tolerances because the thickness of the anisotropic conductive film 36 may be in a range from about 20 to 70 pm, preferably in a range of 30 pm to 50 pm. Therefore, when appropriately depositing the solder materials 16 and 18 on the landing pads 12 and 14 to a sufficient height, taking a thickness of the feature module 30 into account, a recess 29 to a minimal extend may be formed in the prelam body 20 of Fig. 4, reducing the risk of damaging the landing pads 12 and 14 during recessing.

Referring to Figs. 7 to 9, other illustrative embodiments will be described. Figs. 7 to 9 schematically illustrate, in cross sectional views, a process of forming a smart card 200 as shown in Fig. 9 when starting from a prelam body 220 provided at an initial stage during formation of the smart card. The prelam body 220 may be obtained in accordance with techniques as described with regard to the prelam body 20 as described with regard to Fig. 1 to 3 above, the explicit disclosure of which is included by reference in its entirety at this point.

At the stage shown in Fig. 7 and any subsequent stage, the prelam body 220 may be understood as representing a card body as explained above, although this is not explicitly stated below. Particularly, the expression “prelam body 220” in the following description may be replaced by the expression “card body” in a straight forward manner.

Referring to Fig. 7, the prelam body 220 is provided at an early stage during formation of the smart card, which will result in the smart card 200 as shown in Fig. 9. The prelam body 220 comprises a substrate 210 having landing pads 212, 214, 211 and 217. In accordance with some illustrative examples herein, the landing pads 214 and 211 may be connected by a conductive track 213. This does not pose any limitation to the present disclosure and the conductive track 213 may be omitted or may be located at a different position so as to allow for a connection among at least two of the landing pads 212, 214, 211 , 217. Furthermore, there may be a different number of landing pads than the landing pads that are explicitly illustrated in Fig. 7 to 9, e.g., a greater number of landing pads than the landing pads illustrated in the cross sectional views of Fig. 7 to 9.

With continued reference to Fig. 7, a solder material 216 is formed on the landing pad 212, a solder material 218 is formed on the landing pad 214, a solder material 215 is formed on the landing pad 211, and a solder material 219 is formed on the landing pad 217. The solder materials

215, 216, 218 and 219 are formed such that the solder materials 215, 216, 218 and 219 extend to a common height level over the substrate 210. In other words, the solder materials 216, 218, 215 and 219 may have a common thickness provided that the landing pads 211 , 212, 214 and 217 have a common thickness. For example, each of the solder materials 215, 216, 218, and 219 may be formed on the corresponding one of the landing pads 211 , 212, 214, and 217 such that solder material and associated landing pad together may have a height of at least 100 pm after printing and reflow processes are performed. For example, such a height may be given by a total thickness formed by a thickness of a landing pad and a thickness of the solder material.

In accordance with some illustrative examples herein, the solder material 215, 216, 218, and 219 may be deposited via a solder printing process onto the substrate 210. Furthermore, a reflow process may be performed after the solder printing process for reflowing the solder material 215,

216, 218, and 219 on the corresponding landing pads 211 , 212, 214, and 217. In accordance with some illustrative examples herein, printing and reflowing of the solder material 215, 216, 218, and 219 may be easily done in any continuous reel-to-reel process with a desired thickness, e.g., a thickness of at least 100 pm, by screen printing. In accordance with some special illustrative examples herein, the solder materials 215, 216, 218, and 219 may be given by a high temperature solder paste, such as SAC305, for example (which is a solder paste made out of 96.5 weight% Sn, 3.0 weight% Ag, and 0.5 weight% Cu) or the like. Such a solder paste made of SAC305 may have a melting point of about 217°C. This does not pose any limitations of the present disclosure and a high temperature solder paste that has a melting point of at least 160°C may be employed instead. Preferably, the solder material 215, 216, 218, and 219 may have a reflow temperature which is higher than any elevated temperature to which the substrate is exposed during subsequent processing, i.e., an integration of the substrate 210 into the prelam body 220. For example, the solder material 215, 216, 218, and 219 may have a reflow temperature of about 250°C or more.

In accordance with illustrative embodiments, the landing pads 211 , 212, 214 and 217, and the solder materials 215, 216, 218 and 219 are completely embedded into at least one layer 222 of insulating material. Optionally, the substrate 210 may be sandwiched between the at least one layer 222 of insulating material and a lamination layer 224 such that the substrate 210 is completely encapsulated into the prelam body 220. In accordance with some illustrative examples, the at least one layer 222 of insulating material may represent a plurality of different layers of a thermoplastic material which is fused together into a single homogenous sheet body, sealing hermetically the solder material 215, 216, 218, and 219 and the landing pads 211, 212, 214, and 217 on the substrate 210. As possible materials for the at least one layer 222 of insulating material, materials such as PVC, PC, PET-G or Teslin® or stone paper may be used. The at least one layer 222 of insulating material, may be formed on a front side of the substrate, i.e., a side of a substrate 210 on which the landing pads 211, 212, 214, and 217 are arranged. Accordingly, the front side of the substrate 210 may be completely covered by the at least one layer 222 of insulating material.

In accordance with some illustrative embodiments, the substrate 210 may be a flexible substrate as employed in the technology of flexible electronics orflexible circuits. Forexample, the substrate 210 may be a flexible glass-epoxy substrate or a flexible plastic substrate, such as a substrate made of at least one of polyimide, PET, PEN, PC, PVC, and paper. However, this does not pose any limitation to the present disclosure and the substrate 210 may be a substrate as employed in the techniques of printed circuit boards, i.e., a rigid substrate.

In accordance with some illustrative embodiments of the present disclosure, the substrate 210 may comprise an integrated circuit (not shown), the integrated circuit implementing a microprocessor, a memory and/or a crypto processor. The landing pads 211, 212, 214, and 217 may be provided as external contacts to the integrated circuit (not illustrated) integrated into the substrate 210.

For example, in case that the substrate 210 is a flexible substrate, at least one flexible printed circuit (FPC) may be integrated into the substrate 210. The FPC may comprise a base laminate with one or two layers of copper (between 9 pm and 200 pm) and may be made with a photolithographic and chemical etching technology or, in an alternative way with a mechanical punching of the copper foils before lamination on the base laminate.

Referring to Fig. 8, the prelam body 220 is illustrated at a more advanced stage during formation of the smart card 200 as shown in Fig. 9. At the stage illustrated in Fig. 8, a recessing is performed at the prelam body 220, the recessing resulting in recesses 229 and 229’. The recessing exposes upper surfaces 216u and 218u and the recess 229, while upper surfaces 215u and 217u of the solder materials 215 and 217 are exposed in the recess 229’. The recessing may be performed in some illustrative examples herein by a milling, such as a drilling of the recesses 229 and 229’ in a first surface 228 of the prelam body 220, wherein an oppositely arranged second surface 226 is not affected by the recessing. The recessing may include two or more steps of recessing for forming at least the recesses 229 and 229’. A depth of the recess 229 is indicated in Fig. 8 via a line d1. The line d1 indicates a bottom surface of the recess 229. Similarly, a line d2 in Fig. 8 indicates a level of a bottom surface of the recess 229’. The bottom surface 229’b may be subjected to a further milling process, wherein a cavity 229’ is formed in the bottom surface 229’b of the recess 229’. Accordingly, the recess 229’ may have a stepped profile with a stepping between the recess 229’ and the cavity 229”. In other words, a diameter of the recess 229’ may be bigger than a diameter of a cavity 229” when measured in a plane parallel to the bottom surface 229’b.

Referring to Fig. 8, the cavity 229” may at least partially extend through the at least one layer 220 of insulating material towards the substrate 210, may at least partially extend through the substrate 210, and may partially extend into the lamination layer 224. The person skilled in the art will appreciate that the cavity 229” is formed at a location with respect to the substrate 210 such that the landing pads 211 , 217, possibly present conductive tracks and an integrated circuit (not illustrated) integrated into the substrate 210 is not affected by the cavity 229”.

Referring to Fig. 9, the smart card 200 is illustrated at a final stage of formation, wherein a feature module 230 is inserted into the recess 229 and bonded to the prelam body 220, and wherein a feature module 230’ is inserted into the recess 229’ and bonded to the prelam body 220. In particular, the recess 229 accommodates for the feature module 230 such that the first surface 228 is smooth and the feature module 230 snuggly fits into the recess 229. Similarly, the feature module 230’ snuggly fits into the recess 229’ and the first surface 228 is smooth with respect to the prelam body and the feature module 230’. In accordance with some explicit example, the feature module 230’ may be a sensor module having a chip arranged thereon.

In accordance with some illustrative embodiments, the feature module 230 is bonded to the prelam body 220 by means of an anisotropic conductive film provided on one surface of the feature module 230 and electrical connection is obtained via contact pads 232 and 234 on the surface of the feature module 230 covered by the anisotropic conductive film 236. Particularly, the landing pad 212 is electrically and mechanically connected to the contact pad 232 while the landing pad 214 is mechanically connected to the contact pad 234 via the solder material 216, 218, the anisotropic conductive film 236 formed in between. Similarly, the feature module 230’ is electrically and mechanically connected to the landing pads 211 and 217 via the solder material 215 and 219 and an anisotropic conductive film 236’ and 236” formed on a surface of the feature module 230’, thereby connecting the landing pads 211 and 217 with respective contact pads 232’ and 234’ of the feature module 230’.

In accordance with some illustrative embodiments, usage of the anisotropic conductive film 236, 236’, and 236” allows recesses with minimal tolerances because the thickness of each of the anisotropic conductive films 236, 236’, and 236” may be in a range from about 20 to 70 pm, preferably in a range of 30 pm to 50 pm. Therefore, when appropriately depositing the solder material on the landing pads to a sufficient height, taking a thickness of the feature module(s) into account, a recess may be formed to a minimal extend, reducing the risk of damaging the landing pads during recessing. However, instead of at least one of the anisotropic conductive films 236, 236’, and 236”, a solder material may be used, the solder material becoming fusible at a temperature smaller than the temperature at which the solder materials 215, 216, 218, and 219 become fusible. In this case, an additional hot-melt adhesive in order to accommodate the feature modules 230, 230’ into the recesses 229, 229’ of the smart card 200 may be necessary if the solder materials are not enough to reach the required level of adhesion of the feature modules 230, 230’ in the recesses 229, 229’.

With continued reference to Fig. 9, the feature module 230’ may have an electric and/or electronic component 260 electrically and mechanically coupled to the feature module 230’. The electrical and/or electronic component 260 is accommodated into the recess 229’ and the cavity 229”. Accordingly, the feature module 230’may snuggly fit into the prelam body 220 despite the electric and/or electronic component 260 due to the cavity 229”. Accordingly, the electric and/or electronic component 260 maybe coupled via the feature module 230’, particularly the contact pads 232’ and 234’ with the integrated circuit (not illustrated) integrated into the substrate 210 by means of the solder materials 215 and 219 in the electrical and mechanical connection to the landing pads 211 and 217.

Referring to Fig. 9, the smart card 200 shows an electrical interconnection between at least two feature modules 230 and 230’ and the substrate 210 through an electro conductive path created between the feature modules 230 and 230’, the conductive particles of the anisotropic conductive films 236, 236’ and 236” and the solder materials 215, 216, 218 and 219. The feature modules 230 and 230’ may be reliably accommodated into the prelam body 220 despite the different thicknesses and/or sizes of the feature modules 230 and 230’. According to the illustrated example in Fig. 9, the feature module 230’ is integrated into the prelam body 220 and connected to the substrate 210, wherein the contact pads 232’ and 234’ of the feature module 230’ surround the electric and/or electronic component 260 such that a solder connection with a low temperature solder may be realized in some illustrative but not limiting examples. “Low temperature solder” may be a solder material having a melting point at a temperature smaller than a melting point of a high temperature solder and/or a melting point smaller than 250°C, e.g., smaller than 160°C.

In case that the anisotropic conductive films 236, 236’ and 236” are present, the solder material 215, 216, 218 and 219 may be selected as a high temperature solder material. This does not pose any limitations to the present disclosure and the person skilled in the art would appreciate that the anisotropic conductive films 236, 236’ and 236” may be substituted by a solder material formed on the contact pads 232, 234, 232’ and 234’, instead as pointed out above.

Regarding the anisotropic conductive film (ACF) as referred to above, it may be considered as being provided by material constituting a lead-free and environmentally friendly adhesive interconnect system, generally a resin containing conductive particles. ACF technology is used in chip-on-glass (COG), flex-on-glass (FOG), flex-on-board (FOB), flex-on-flex (FOF), chip-on-flex (COF), chip-on-board (COB), and similar applications for higher signal densities and smaller overall packages. An anisotropic conductive paste (when the ACF material is provided in form of a paste) is typically used only in chip-on-flex (COF) applications with low densities and cost requirements, such as for RFID antennas, or in FOF and FOB assemblies in handheld electronics. In all cases, the anisotropic material, for example, a thermosetting resin containing conductive particles, is first deposited on the base substrate (here a feature module) via a lamination process for ACF or a dispense process for ACP or a printing process for ACP. The device or secondary substrate (here the prelam body) is then placed in position over the base substrate and the two sides are pressed together to mount the secondary substrate or device to the base substrate. In many cases, this mounting process is done with no heat or a minimal amount of heat that is just sufficient to cause the anisotropic material to become slightly tacky. In the case of using a thermosetting resin containing conductive particles, the particles are trapped between prominent points, such as electrodes, between the substrate and the component, thereby creating an electrical connection therebetween. Other particles are insulated by the thermosetting resin. In some cases, this mounting step is skipped and the two sides go directly to the bonding portion of the process. In high volume manufacturing, however, this would lead to inefficiencies in the manufacturing process, so direct bonding is usually done only in the lab or in small scale manufacturing. Bonding is the third and final process required to complete an ACF assembly. In the first two processes the temperatures can range from ambient temperature to 100°C, with the heat applied for 1 second or less. For bonding, the amount of thermal energy required is higher due to the need to first flow the adhesive and allow the two sides to come together into electrical contact, and then to cure the adhesive and create a lasting reliable bond. The temperatures, times, and pressure required for these processes can vary depending on the material involved. For example, when considering FOG, an epoxy as an adhesive is used, and process time, process temperature, and process pressure are given by 10-12s, 170-200°C, and 2-4MPa. When considering COG, an epoxy as an adhesive is used, and process time, process temperature, and process pressure are given by 5-7s, 190-220°C, and 50-150MPa. When considering COF, an epoxy as an adhesive is used, and process time, process temperature, and process pressure are given by 5-10s, 190-220°C, and 30-150MPa. When considering FOB, an epoxy as an adhesive is used, and process time, process temperature, and process pressure are given by 10-12s, 170-190°C, and 1-4MPa. When considering FOB, an acrylic resin may alternatively be used as an adhesive, and process time, process temperature, and process pressure are given by 5-10s, 130-170°C, and 1-4MPa. When considering FOF, an epoxy as an adhesive may be used, and process time, process temperature, and process pressure are given by 10-12s, 170-190°C, and 1-4MPa. Alternatively, an acrylic resin may be used for FOF, process time, process temperature, and process pressure being given by 5-10s, 130-170°C, and 1- 4MPa. Herein, pressures for flex assemblies (FOG, FOB, FOF) are measured across the entire area under the bondhead and pressures for chip assemblies (COG, COF) are calculated on the cumulative surface area of the bumps on the chip.

In the description of embodiments according to the brief summary and the description to Fig. 1 to 9 above, when referring to an “anisotropic conductive film”, it is understood that this may also refer to an anisotropic conductive paste (ACP), although ACP may be thicker when deposited on a surface than ACF.

In the description above, when referring to a recessing in the prelam body, the person skilled in the art will appreciate that, as an illustrative but not limiting example, a card milling process may be employed.

In some illustrative examples, a feature module may be given by an ISO module having a thickness of about 190 pm or a fingerprint sensor module having a thickness of about 110 pm without chip.

In summary of the above, the present invention may provide for a smart card having at least one feature module integrated therein. Herein, a substrate having at least one first landing pad formed thereon is prepared, a solder material is formed on the at least one first landing pad, the substrate with the solder material on the at least one first landing pad is integrated into a prela body, wherein the substrate is arranged at a first surface of the prelam body, the prelam body is recessed at a second surface of the prelam body opposite the first surface, wherein an upper surface of the solder material on the at least one first landing pad is exposed in a first recess of the prelam body, a first feature module is inserted into the first recess of the prelam body, and the first feature module inserted into the first recess is bonded to the prelam body so as to electrically connect the at least one first landing pad to the first feature module via the solder material.

Claims

1. A method of forming a smart card having at least one feature module integrated therein, the method comprising: preparing a substrate having at least one first landing pad formed thereon; forming a solder material on the at least one first landing pad; integrating the substrate with the solder material on the at least one first landing pad into a prelam body, the substrate being arranged at a first surface of the prelam body; recessing the prelam body at a second surface of the prelam body opposite the first surface, wherein an uppers surface of the solder material on the at least one first landing pad is exposed in a first recess of the prelam body; inserting a first feature module into the first recess of the prelam body; and bonding the first feature module inserted into the first recess to the prelam body so as to electrically connect the at least one first landing pad to the first feature module via the solder material.

2. The method of claim 1, the method further comprising providing the first feature module with an anisotropic conductive film on the surface of the first feature module covering at least one contact pad provided in the surface prior to inserting the first feature module into the first recess, and bringing the anisotropic conductive film into contact with the exposed upper surface of the solder material on the at least one first landing pad when inserting the first feature module into the first recess.

3. The method of claim 2, wherein the bonding of the first feature module to the prelam body comprises curing the anisotropic conductive film in the first recess at an elevated temperature of at least 160°C.

4. The method of claim 3, wherein the first feature module is subjected to a bonding pressure when curing the anisotropic conductive film.

5. The method of one of claims 2 to 4, wherein the solder material is a high-temperature solder material fusible at temperatures greater than 160°C.

6. The method of one of claims 1 to 5, wherein the first feature module has at least one first contact pad exposed on a surface of the first feature module, the method further comprising aligning the at least one first contact pad of the first feature module to the at least one first landing pad of the prelam body prior to inserting the first feature module into the first recess.

7. The method of one of claims 1 to 6, wherein a height of the solder material and the at least one first landing pad is at least 100 pm.

8. The method of one of claims 1 to 7, further comprising: forming at least one second landing pad in electrical contact with the integrated circuit on the substrate and forming a solder material on the at least one second landing pad prior to integrating the substrate into the prelam body; recessing the prelam body at the second surface of the prelam body for forming a second recess in the prelam body, wherein an upper surface of the solder material on the at least one second landing pad is exposed in the second recess; inserting a second feature module into the second recess of the prelam body; and bonding the second feature module inserted into the second recess to the prelam body.

9. The method of claim 8, wherein the first and second feature modules are of different thicknesses, the first recess having a first depth and the second recess having a second depth different from the first depth, and wherein the first and second depths is such that the first and second feature modules are accommodated into the first and second recesses so as to realize a smooth surface of a body of the smart card at the first and second feature modules.

10. The method of claim 8 or 9, wherein the solder material on the at least one first and second landing pad has a common height in the prelam body prior to the recessing.

11. The method of one of claims 8 to 10, the method further comprising providing the second feature module with an anisotropic conductive film on the surface of the second feature module prior to inserting the second feature module into the second recess, and bringing the anisotropic conductive film into contact with the exposed upper surface of the solder material on the at least one second landing pad when inserting the second feature module into the second recess.

12. The method of claim 11 , wherein the bonding of the second feature module to the prelam body comprises curing the anisotropic conductive film in the second recess at an elevated temperature of at least 160°C.

13. The method of claim 12, wherein the second feature module is subjected to a bonding pressure when curing the anisotropic conductive film.

14. The method of one of claims 11 to 13, wherein the solder material is a high-temperature solder material fusible at temperatures greater than 160°C.

15. The method of one of claims 8 to 14, wherein the second feature module has at least one second contact pad exposed on a surface of the second feature module, the method further comprising aligning the at least one second contact pad of the second feature module to the at least one second landing pad of the prelam body prior to inserting the second feature module into the second recess.

16. The method of one of claims 8 to 15, wherein a height of the solder material and the at least one second landing pad is at least 100 pm.

17. The method of one of claims 1 to 16, wherein the substrate is a flexible substrate having an integrated circuit formed therein.

18. A prelam body, comprising: a substrate at a first surface of the prelam body, the substrate having at least one first landing pad and a solder material disposed on the at least one landing pad; at least one layer of insulating material into which the at least one first landing pad and the solder material is completely embedded; and a first recess formed in a second surface of the prelam body, the second surface being opposite to the first surface, wherein the first recess only exposes an upper surface of the solder material on the at least one first landing pad.

19. The prelam body of claim 18, wherein the substrate is a flexible substrate having an integrated circuit formed therein.

20. The prelam body of claim 18 or 19, further comprising: at least one second landing pad formed on the substrate and a solder material disposed on the at least one second landing pad; and a second recess formed in the second surface, the second recess only exposing an upper surface of the solder material on the at least one second landing pad.

21. The prelam body of claim 20, wherein the first recess has a first depth and the second recess has a second depth, the first and second depths being different from each other.

22. A smart card, comprising: the prelam body of claim 18 or 19; and a first feature module having an anisotropic conductive film formed on a surface of the first feature module, wherein the first feature module is accommodated into the first recess such that the exposed upper surface of the solder material in the first recess is covered by the anisotropic conductive film.

23. The smart card of claim 22, wherein a height of the solder material together with the at least one first landing pad is in the range from about 50 pm to about 250 pm.

24. The smart card of one of claims 22 and 23, further comprising a lamination layer covering the first surface of the prelam body such that the substrate is sandwiched between the lamination layer and the at least one insulating layer, and an electrical component, the electrical component being arranged on the surface of the first feature module, wherein the first recess has a cavity formed at a portion of a bottom surface of the first recess, the cavity extending at least partially through the substrate and accommodating the electrical component, wherein the electrical component is left uncovered by the anisotropic conductive film.

25. A smart card, comprising: the prelam body of claim 20 or 21 ; and a second feature module having an anisotropic conductive film formed on a surface of the second feature module, wherein the second feature module is accommodated into the second recess such that the exposed upper surface of the solder material in the second recess is covered by the anisotropic conductive film.

26. The smart card of claim 25, wherein a height of the solder material together with the at least one second landing pad is in the range from about 50 pm to about 250 pm.

27. The smart card of one of claims 22 to 26, wherein the solder material is a high-temperature solder material fusible at temperatures greater than 160°C.